Λ: Ground Mode of the Cosmic Boundary

Einstein introduced Λ cosmological constant in 1917 to hold the universe static. When Hubble proved the universe was expanding, Einstein removed it, calling it his "biggest blunder." A century later, standard cosmology revived Λ as dark energy, a mysterious force accelerating expansion; Einstein vindicated, but for a different reason. Mode Identity Theory completes the arc: there is no dark energy nor mysterious force. Λ is the ground-state modal realization on the cosmic boundary; the geometry of the universe itself driving expansion. Einstein was right the first time, for reasons then unknown. The Möbius surface selects half-integer modes; the lowest yields the modal realization Λ_top · ℓ_P² ≈ 2Ω⁻¹. The observationally inferred Λ_obs differs by an inherent factor of 3/2 when converting from 2D surface to 3+1 spacetime. Prediction: 3.0 × 10⁻¹²². Observed: 2.84 × 10⁻¹²². Agreement: ~5%. No free parameters.v2 update: for framing and mathematical rigor. Core derivations and predictions unchanged.